R/pwr.anova.test.R

In pwr: Basic Functions for Power Analysis

"pwr.anova.test" <-
function (k = NULL, n = NULL, f = NULL, sig.level = 0.05, power = NULL)
{
    if (sum(sapply(list(k, n, f, power, sig.level), is.null)) !=
        1)
        stop("exactly one of k, n, f, power, and sig.level must be NULL")
    if (!is.null(f)){
        if (is.character(f))
            f <- cohen.ES(test="anov",size=f)$effect.size
        if (any(f < 0))
            stop("f must be positive")
    }
    if (!is.null(k) && any(k < 2))
        stop("number of groups must be at least 2")
    if (!is.null(n) && any(n < 2))
        stop("number of observations in each group must be at least 2")
    if (!is.null(sig.level) && !is.numeric(sig.level) || any(0 >
        sig.level | sig.level > 1))
        stop(sQuote("sig.level"), " must be numeric in [0, 1]")
    if (!is.null(power) && !is.numeric(power) || any(0 > power |
        power > 1))
        stop(sQuote("power"), " must be numeric in [0, 1]")
    p.body <- quote({
        lambda <- k * n * f^2
        pf(qf(sig.level, k - 1, (n - 1) * k, lower = FALSE),
            k - 1, (n - 1) * k, lambda, lower = FALSE)
    })
    if (is.null(power))
        power <- eval(p.body)
    else if (is.null(k))
        k <- uniroot(function(k) eval(p.body) - power, c(2 + 1e-10, 100))$root
    else if (is.null(n))
        n <- uniroot(function(n) eval(p.body) - power, c(2 + 1e-10, 1e+09))$root
    else if (is.null(f))
        f <- uniroot(function(f) eval(p.body) - power, c(1e-07, 1e+07))$root
    else if (is.null(sig.level))
        sig.level <- uniroot(function(sig.level) eval(p.body) - power,
            c(1e-10, 1 - 1e-10))$root
    else stop("internal error")
    NOTE <- "n is number in each group"
    METHOD <- "Balanced one-way analysis of variance power calculation"
    structure(list(k = k, n = n, f = f, sig.level = sig.level,
        power = power, note = NOTE, method = METHOD), class = "power.htest")
}